1. Field of the Invention
The present invention relates generally to an integrated access device (IAD) system based on ADSL (Asymmetric Digital Subscriber Line), and in particular, to a home network system that can be built using a two-wire telephone line in a home.
2. Description of the Related Art
ADSL is a high-speed data transmission system operating in an unoccupied higher frequency band of the frequency band of an existing plain old telephone network without interrupting the voice-transmitting Telephone service. The ADSL compresses data received from the Internet to a signal of 1 Mbps or above and transmits the compressed signal to a distributor in a home via a two-wire telephone line. The distributor separates voice and data from the input signal and distributes the voice to a telephone and the data to a computer after decompression. The ADSL system is so configured that one modem is confined to one PC (Personal Computer) in the home. This typical ADSL system is shown in FIG. 1.
Referring to FIG. 1, the typical ADSL system is comprised of an ADSL multiplexer (MUX) 103, a plurality of first distributors 105, and a plurality of homes 110-1, 110-2, and 110-3 connected to each first distributor 105.
The ADSL MUX 103, connected to the Internet, compresses data received from the Internet in a predetermined method and outputs the compressed data to the first distributors 105. The ADSL MUX 103 decompresses compressed data received from the first distributors 105 in accordance with an Internet protocol and outputs the decompressed data to the Internet.
The first distributor 105 shown in FIG. 1 is connected to a central office 101 via a telephone line and to the ADSL MUX 103 via an optical cable. The first distributor 105 combines an input voice signal with compressed Internet data for each home and distributes the combined signal to the home. Hereinafter, the signal of voice and compressed data combined is referred to as an ADSL signal. Specifically, the first distributor 105 transmits data received from the ADSL MUX 103 to a PSTN (Public Switched Telephone Network) subscriber in an upper frequency band of the frequency band of the PSTN. Since 0–4.3 KHz in the PSTN frequency band is generally allocated for the telephone service, a 30 KHz or above frequency band other than the telephone service frequency band is available for data transmission. The data transmission frequency band is divided into an upstream region and a downstream region to separately perform data transmission and data reception. That is, the first distributor 105 loads compressed Internet data in an upper frequency band of the PSTN frequency band in which a voice signal for a specific subscriber has been loaded and transmits the ADSL signal to the subscriber via a corresponding telephone line. On the other hand, the first distributor 105 collects ADSL signals from the homes 110-1, 110-2, and 110-3, separates a voice signal and compressed Internet data from each ADSL signal, and outputs the compressed data to the ADSL MUX 103 and the voice signal to the central office 101.
Each home includes a second distributor 111 connected to the first distributor 105, for separating a voice signal and compressed Internet data from an ADSL signal received from the first distributor 105, combining a voice signal received from a telephone 115 or 127 with input compressed Internet data, and transmitting the ADSL signal to the first distributor 105. An ADSL modem 113 connected to the second distributor 111, for decompressing the compressed Internet data received from the second distributor 111 and outputting the decompressed data to a computer 119, and compressing data received from the computer 119 and outputting the compressed data to the second distributor 111. The telephone 115 or 127 receives the same voice signal from the second distributor 111 and performs a normal call process.
Because the conventional ADSL system employs a point-to-point scheme, a subscriber is limited to one speech path and one data communication line for one telephone number. If two or more persons are to establish their respective speech paths for separate calls, two telephone lines are required. Similarly, if two or more persons want data communication at the same time, a LAN (Local Area Network) for home in addition to the ADSL system is required.